Process for Coating Metal Components With a Coating That Prevents Electrochemical Plating

ABSTRACT

The present invention is directed to a method of coating metal articles with a flexible, chemical-resistant, corrosion-resistant, and abrasion-resistant coating that can be optionally formed and optionally electroplated. In some examples, the articles are metal motor vehicle bumpers.

RELATED APPLICATION

This Application claims the benefit of U.S. Provisional Application61/349,566 filed on May 28, 2010, which is entirely incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention is directed to a method of coating metal articleswith a flexible, chemical-, corrosion-, and abrasion-resistant coatingthat can be optionally formed and optionally electroplated. In someexamples, the articles are metal motor vehicle bumpers.

BACKGROUND OF THE INVENTION

In the manufacturing of a plated article, the traditional technique isto form a flat metal sheet into the desired shape, and then clean,plate, and paint the surface. For example, in traditional manufacturingof a metal motor vehicle bumper (e.g., a chrome bumper for automobilesand trucks), a sheet of untreated metal is formed into the desiredbumper shape using multistep metal stamping and pressing processes tocreate a three dimensional article that has bends and curves. The formedmetal is then polished and electrochemically cleaned by passing itthrough acidic and alkaline chemical baths to remove any dirt, oils,lubricants, drawing fluids, and processing residue. The front surface,which is the outer side of the finished and installed bumper, iselectroplated with one or more layers of metal, for example nickel andchromium. The back surface, which is the inner side of the finished andinstalled bumper, is plated as well when the formed bumper is immersedin metal baths during the plating process. After plating, a back sidecoating is applied to cover the residual metal on the back surface.Typically, this back side coating is a dark, fast-curing paint or waxthat is applied by spraying by hand on the formed article, which resultsin overspray on the front plated surface. This is then removed from theelectroplated front surface by hand before the bumper is installed.

A coating that is anti-corrosive is necessary for metal articles, suchas the back side of electroplated metal bumpers, because corrosion andrust can result in unsightly dripping or staining onto the trim elementsof the motor vehicle. Corrosion also weakens the structural integrity ofthe bumper. While electrochemical plating provides corrosion resistance,plating the back side potentially increases production costs, because itdeposits expensive metallic layers on a surface that it not exposed toview.

Thus, a need remains for a method of coating a metal article with achemical-, corrosion-, and abrasion-resistant coating that is flexibleenough to withstand optional formation into a desired shape and optionalelectroplating with one or more additional coatings.

SUMMARY OF THE INVENTION

These and other needs are met by the present invention, which isdirected to a method of coating the surface of a metal article. Thecoating comprises a novel method of painting the back side of a flatmetal sheet, before forming, with a coating that is chemical-,corrosion-, and abrasion-resistant. In addition, the coating is flexibleenough to withstand optional forming with multistep metal pressing andstamping processes. The coating also resists electroplating, when anuncoated surface of the metal article is to be optionally electroplated.The coating is comprised of a pretreating compound, a sealer, a primer,and a top coat. This coating method reduces the overall cost ofmanufacturing a metallic plated article by reducing the consumption orexpensive metals on the back side and eliminating several coating stepsthat require manual application and removal. The method can be used inthe manufacturing of formed metal articles, such as a metal motorvehicle bumper.

The coating of the present invention also adds and enhancescorrosion-resistance, which is particularly desirable in metal motorvehicle bumpers, as corrosion can cause unsightly dripping or stainingonto the trim elements of the motor vehicle and degradation of thestructural integrity of the bumper. Corrosion resistance is alsodesirable in other metal articles, for example, motor vehicle mirrorsand other trim elements.

In the manufacturing of metal motor vehicle bumpers, the flat metalsheet will ultimately be formed into a three dimensional metal bumper.Once formed, the front side is the outer side of the finished andinstalled bumper, which will be the target for electrochemical platingwith one or more metallic layers. The back side of the motor vehiclebumper is the inner side of the finished and installed bumper, whichwill be the target for coating according to the present invention.

The coating of the present invention also provides abrasion-resistance,which is particularly important in the forming process of metalarticles. For example, in forming a metal bumper, the metal sheet issubjected to multistep stamping and pressing processes that can deliverseveral tons of force. The coating of the present invention is notcompromised during this stamping process, and it maintains completeadhesion to the metal. Thus, the coating is abrasion-resistant, and itwill not be scraped off during the forming process.

The method of the present invention is possible through a variety ofcombinations or surface preparations and coating layers that result in acoated metal article. Common to each series of coating layers is ageneral method that encompasses the various steps of the presentinvention. Thus, in one aspect, the invention relates to a method ofcoating the surface of a metal article, comprising the steps of:

-   -   a. cleaning the metal surface with one or more alkaline        cleaners;    -   b. pretreating the metal surface with one or more        phosphate-containing pretreating compounds;    -   c. applying one or more corrosion-resistant sealers to the metal        surface;    -   d. applying one or more corrosion-resistant primers to the metal        surface; and    -   e. applying one or more chemical- and corrosion-resistant top        coats to the metal surface,

wherein the resulting metal surface is chemical-, corrosion-, andabrasion-resistant.

In a further aspect, the invention relates to a method of coating thesurface of a metal article, comprising the steps of:

-   -   a. cleaning the metal surface with Betz Kleen 132® or 111 Low        Foam Cleaner®;    -   b. pretreating the metal surface with one or more pretreating        compounds selected from the group consisting of Permatreat®        1510, Permatreat® 2105, Bonderite 902, Bonderite 2010, ChemCote        3010, Gardobond 51/2, and Permatreat® 407;    -   c. applying Bonderite 1455 SF to the metal surface;    -   d. applying a polyester resin primer system that contains        hydroxyl groups that are crosslinked with blocked or unblocked        isocyanates; and    -   e. applying a PVC plastisol top coat coating,

wherein the resulting metal surface is chemical-, corrosion-, andabrasion-resistant.

In a further aspect, the invention relates to a metal motor vehiclebumper, wherein the metal bumper characterized by a surface that is:

-   -   a. cleaned with Betz Kleen 132® or 111 Low Foam Cleaner®;    -   b. pretreated with one or more pretreating compounds selected        from the group consisting of Permatreat® 1510, Permatreat® 2105,        Bonderite 902, Bonderite 2010, ChemCote 3010, Gardobond 51/2,        and Permatreat® 407;    -   c. sealed with Bonderite 1455 SF;    -   d. coated with a polyester resin primer system that contains        hydroxyl groups that are crosslinked with blocked or unblocked        isocyanates; and    -   e. coated with a PVC plastisol top coat;    -   wherein the resulting metal motor vehicle bumper has a        chemical-, corrosion-, and abrasion-resistant coating.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a production flowchart that illustrates a manufacturingprocess for making a metal motor vehicle bumper.

DETAILED DESCRIPTION OF THE INVENTION Embodiments

As indicated, one aspect of the invention is directed to a method ofcoating the surface of a metal article. First, the metal is cleaned withone or more alkaline cleaners. Next, the metal is pretreated with one ormore phospate-containing pretreating compounds. Then, one or morecorrosion-resistant sealers are applied to the metal surface, followedby one or more corrosion-resistant primers. Finally, a chemical- andcorrosion-resistant top coat is applied to the metal surface.

Type of Metal Articles

Choosing a metal is depicted as Step 10 of FIG. 1. The coating of theinvention can be applied to the surfaces of a wide variety of metals.Thus, in one embodiment, the coating can be applied to a pre-formedmetal article. In another embodiment, the metal is a metal blank. Inanother embodiment, the metal is a metal blank that has a thicknessbetween 0.001 and 5 inches. More particularly, the metal is a metalblank that has a thickness between 0.005 and 1 inch. In anotherembodiment, the metal blank has a thickness between 0.001 and 0.250inch. More particularly, the metal blank has a thickness between 0.020and 0.150 inch.

In another embodiment, the metal blank can eventually be subject topost-coating formation.

The metal chosen will depend on the end use of the metal article. In oneembodiment, the metal is a metal blank that will ultimately be formedand plated for use as a motor vehicle bumper or bumper accessory.

In one embodiment, the metal article is selected from the groupconsisting of brushed or unbrushed hot rolled steel, brushed orunbrushed cold rolled steel, and brushed or unbrushed high strengthsteel, or the like. More particularly, the metal is cold rolled steel.Alternatively, the metal is selected from the group consisting ofDrawing Steel (ASTM Specifications A1008 and A1011), Deep Drawing Steel(ASTM Specification A1008), Extra Deep Drawing Steel (ASTM Specification1008), and High Strength Low Alloy Steel (ASTM Specifications A606 andA1008), or the like.

In one embodiment, the metal surface is pickled via techniques readilyavailable in the art, including, but not limited to, treatment with apickling liquor containing a strong acid, such as a mineral acidselected from the group consisting of sulfuric acid, hydrochloric acid,and mixtures thereof, or the like. In another embodiment, the metalsurface is nonpickled.

Grinding the Surface of the Metal Article

In one embodiment, the surface of the metal article to be coated may beslightly ground, using methods known in the art, to remove anyproduction residue and oil or grease coating that may have been appliedto prevent or minimize corrosion during shipment and storage. Themechanical grinding process may be dry or wet using water. Thismechanical grinding process will also provide an abraded surface thatwill increase the adherence of the coating layers. The material used togrind can be, for example, but not limited to, sandpaper, syntheticwoven mesh, brushes, and combinations thereof, or the like. Grinding thesurface of the metal is depicted as Step 20 in FIG. 1.

Cleaning the Surface of the Metal Article

The surface of the metal article to be coated is then cleaned to removeany residue that is present on the surface. This is shown as Step 30 inFIG. 1. A variety of cleaners may be used. In one embodiment, thecleaner is an alkaline cleaner. More particularly, the cleaner isselected from the group consisting of Betz Kleen 132®, 111 Low FoamCleaner® (available from Torch Surface Technologies), and mixturesthereof, or the like.

In one embodiment, the cleaning step is accomplished by any cleaningmethod known in the art, for example, but not limited to, in a vat, bysurface spraying or scrubbing, and combinations thereof, or the like.More particularly, the surface of the metal article is cleaned bysurface spraying and scrubbing. After the cleaning step is complete, themetal article must be completely dried by any drying method known in theart, for example, but not limited to, air drying.

Pretreating the Surface of the Metal Article

After cleaning, the surface of the metal article to be coated ispretreated using a phosphate-containing pretreating compound to improvepaint adhesion and minimize the risk of corrosion. This is depicted asStep 40 in FIG. 1. Examples of pretreatment compounds include, but arenot limited to, chromic phosphate, ferrous phospate, ferric phosphate,zinc phosphate, and mixtures thereof, or the like. More particularly,the pretreating compound is selected from the group consisting ofPermatreat® 1510 (available from Betz Laboratories, Inc.), Permatreat®2105 (available from Betz Laboratories, Inc.), Bonderite 902 (availablefrom Henkel Corporation), Bonderite 2010 (available from HenkelCorporation), ChemCote 3010 (available from Chemetall and Oakite),Gardobond 51/2 (available from Chemetall and Oakite), Permatreat® 407(available from Betz Laboratories, Inc.), and mixtures thereof, or thelike.

The metal article should be completely dry before the pretreatmentcompound is applied. The pretreatment compound can be applied by anymethod known in the art, including, but not limited to, spraying,dipping, brush coating, roll coating, and combinations thereof, or thelike. In one embodiment, the coating weight will generally be between10-100 mg/ft². More particularly, the pretreatment layer has a coatingweight of 20-45 mg/ft².

More than one pretreatment compound can be applied to the metal surfaceif necessary based on the end use of the metal article. Differentpretreatment compounds may be used depending on the type of metal, theend use of the metal article, and the other layers of the coating.

Sealing the Surface of the Metal Article

An anti-corrosion sealer is then applied to the surface of the metalarticle, as shown by Step 50 in FIG. 1. The sealer can also improvepaint adhesion to the metal. Appropriate sealers are generally chrome ornon-chrome. In one embodiment, a chrome sealer is applied. Examples ofchrome sealers include, but are not limited to, Betz Sealguard™(available from Betz Laboratories, Inc.), Bonderite 1402W (availablefrom Henkel Corporation), Gardobond C 4571 (available from Chemetall),and mixtures thereof, or the like. In another embodiment, a non-chromesealer is applied. Examples of non-chrome sealers include, but are notlimited to, Betz® DC2068 (available from Betz Laboratories, Inc.),Bonderite 1455 SF (available from Henkel Corporation), and mixturesthereof, or the like. More particularly, in one embodiment, the sealeris Bonderite 1455 SF.

The sealer may be applied by any method known in the art, including, butnot limited to, spraying, dipping, brush coating, roll coating, andcombinations thereof, or the like. In one embodiment, more than onesealer can be applied to surface of the metal article if necessary basedon the end use of the metal article. In one embodiment, the sealer has acoating weight of 2-50 mg/ft². More particularly, in one embodiment, thesealer has a coating weight of 4-16 mg/ft².

Different sealers will be used depending on the type of metal, end useof the metal article, and the additional components used in the coating.In one embodiment, more than one sealer is applied to the metal surface.The sealer may be allowed to dry completely after application.

Priming the Surface of the Metal Article

The surface of the metal article is then primed with a primer havingflexibility, chemical-resistance, corrosion-resistance, andabrasion-resistance. This step is depicted as Step 60 in FIG. 1. Thechosen primer will depend on the end use of the metal article. Suitableprimers include, but are not limited to, water borne primers, solventborne primers, liquid solvent borne high solids primers, powder coatingprimers, and mixtures thereof, or the like. More particularly, in oneembodiment, the primer is based on a material selected from the groupconsisting of thermoplastic acrylic, polyester, polyvinyl, polyepoxy,polyurethane, polyamide, polyamine, acrylic carbamate resin systems, andmixtures thereof, or the like. In another embodiment, the primer isselected from the group consisting of UV and Electron Beam curedcoatings, or the like.

In one embodiment, the primer is a thermosetting composition with acurable resin that has functional groups. More particularly, thosefunctional groups that are selected from the group consisting ofhydroxyl, carboxylic acid, carbamate, anhydride, amine, epoxy, amide,carbonate, and mixtures thereof, or the like. In one embodiment, thefunctional groups of the curable resin are reacted with a crosslinkingagent to form a crosslinked network. More particularly, the crosslinkingagent is selected from the group consisting of isocyanates, blockedisocyanates, aminoplasts, melamines, epoxies, anhydrides, and mixturesthereof, or the like. More particularly, in one embodiment, the primeris a polyester resin system that contains hydroxyl groups that arecrosslinked with blocked or unblocked isocyanates.

In another embodiment, the viscosity of a solvent borne primer isadjusted with a standard organic solvent. More particularly, theviscosity of a solvent borne primer is adjusted with a standard organicsolvent selected from the group consisting of ketones, acetates, nonpolar aliphatic hydrocarbons, polar aliphatic hydrocarbons, polararomatic solvents, non-polar aromatic solvents, alkyl polyethers, alkylpolyether acetates, and mixtures thereof, or the like. The finalviscosity of the primer is measured using a Zahn #2 viscosity cup at atemperature of 70° F. The viscosity of the primer is 20-40 seconds. Moreparticularly, the viscosity of the primer is 28-32 seconds.

The primer can be pigmented with one or more pigments to achieve adesired color and improve corrosion resistance. The primer may containchrome or non-chrome pigments. In one embodiment, the pigment isnon-chrome. More particularly, the pigment is chosen from the groupconsisting of organic or inorganic compounds or colored materials,fillers, metallic or other inorganic flake materials, and mixturesthereof, or the like. Examples of pigments include, but are not limitedto, carbon black pigment, titanium dioxide, iron oxide, chrome yellow,moly orange, titanium yellow, nickel titanate yellow, chrome green,phathalo blue, phathalo green, perylene red, magenta red, and mixturesthereof, or the like. In one embodiment, more than one pigment isapplied to the metal surface.

The primer is applied using a method known in the art, including, butnot limited to, air atomized spray, air assisted airless spray, airlessspray, HVLP spray, electrostatic rotary bell spray, electrostatic airatomized spray, electrostatic air assisted airless spray, electrostaticHVLP spray, direct roll coating, reverse roll coating, flow coating,dipping, curtain coating, and combinations thereof, or the like. The dryfilm thickness of the primer should be about 2.5 to 50 microns. Moreparticularly, the primer has a dry film thickness of 10 microns to 20microns.

The primer is completely cured after application using methods known inthe art, including, but not limited to, heating and UV light. In oneembodiment, the primer is cured by a method selected from the groupconsisting of a heating means, short or medium long wave infrared light,and a combination of a heating means and infrared light. In oneembodiment, the primer is cured using a heating means with ovens thatreach a peak metal temperature of 370-450° F., with an oven dwell timeof 30-300 seconds. More particularly, the primer is cured using aheating means with ovens that reach a peak metal temperature of 400-420°F., with an oven dwell time of 60-180 seconds. In one embodiment, theheating means is an electric or natural gas convection oven.

A completely cured primer gives 5-75 methyl ethyl ketone double rubs,according to ASTM Test Method D5402-06. More particularly, the curedprimer gives 5-50 methyl ethyl ketone double rubs, according to ASTMTest Method D5402-06.

Applying a Top Coat to the Surface of the Metal Article

A top coat is then applied to the surface of the metal article, as shownby Step 70 in FIG. 1. The chosen top coat must adhere to the primerlayer below it, be flexible, chemical-resistant, andcorrosion-resistant. The chosen top coat will depend on the end use ofthe metal article. In one embodiment, the top coat is selected from thegroup consisting of thermoplastic or thermoset water borne, solventborne, solvent borne high solid, powder coating based on acrylic,polyester, epoxy, urethane, polyamide, polyamine, carbamate,polyvinylidine fluoride resin systems, and mixtures thereof, or thelike. In one embodiment, thermoset top coats are crosslinked withisocyanates, blocked isocyanates, melamines, epoxies, and mixturesthereof, or the like. More particularly, in another embodiment, the topcoat is selected from the group consisting of colloidal dispersions ofpolyvinyl chloride, formulated with the appropriate plasticizers thatwill give the desired film properties. More particularly, theplasticizers are phthalate or non-phthalate based materials.

In another embodiment, the top coat is selected from the groupconsisting of UV and Electron Beam cured coating, or the like.

A non-limiting example of a suitable top coat is a PVC plastisolcoating, which is prepared by emulsion or microemulsion polymerizationin plasticizers and solvents. Upon heating or curing, the plasticizersdiffuse into the dispersed polymer particles, inducing plasticization ofthe coating. The resulting coating is highly elastic, abrasionresistant, chemical-resistant, and dimensionally stable.

In another embodiment, the viscosity of a solvent borne top coat isadjusted with a standard organic solvent. More particularly, theviscosity of a solvent borne top coat is adjusted with nonpolar mineralspirits or a standard organic solvent selected from the group consistingof ketones, acetates, non polar aliphatic hydrocarbons, polar aliphatichydrocarbons, polar aromatic solvents, non-polar aromatic solvents,alkyl polyethers, alkyl polyether acetates, and mixtures thereof, or thelike. In one embodiment, the viscosity can be adjusted with a solventselected from the group consisting of Aromatic 100, 150, and 200(available from Exxon Mobil), and mixtures thereof, or the like. Thefinal viscosity of the topcoat is measured using a Zahn #4 viscosity cupat a temperature of 70° F. The viscosity of the reduced topcoat is 15-40seconds. More particularly, the viscosity of the reduced topcoat is22-27 seconds.

The chosen top coat can be pigmented with one or more pigments toachieve a desired color. In one embodiment, the colored pigment isinorganic. More particularly, the colored pigment is an inorganicpigment selected from the group consisting of zinc white, zinc sulfide,carbon black, iron manganese black, spinel black, chromium oxide,chromium oxide hydrate green, cobalt green, ultramarine green, cobaltblue, ultramarine blue, manganese blue, ultramarine violet, cobaltviolet, manganese violet, red iron oxide, molybdate red, ultramarinered, brown iron oxide, mixed brown iron oxide, yellow iron oxide, nickeltitanium yellow, chromium titanium yellow, cadmium sulfide, cadmium zincsulfide, chromium yellow, bismuth vanadate, and mixtures thereof, or thelike.

In another embodiment, the colored pigment is organic. Moreparticularly, the colored pigment is an organic pigment selected fromthe group consisting of monoazo pigments, diazo pigments, anthraquinonepigments, bexnzimidazole pigments, quinacridone pigments, quinophthalonepigments, diteopyrrolopyrrole pigments, dioxzine pigments, indanthronepigments, isoindolien pigments, isoindolinone pigments, azomethinepigments, perinone pigments, perylene pigments, phthalocyanine pigments,aniline black, and mixtures thereof, or the like.

The top coat is applied using a method known in the art, including, butnot limited to, air atomized spray, air assisted airless spray, airlessspray, HVLP spray, electrostatic rotary bell spray, electrostatic airatomized spray, electrostatic air assisted airless spray, electrostaticHVLP spray, direct roll coating, reverse roll coating, flow coating,dipping, curtain coating, and combinations thereof, or the like. The topcoat should have a dry film thickness of 2.5-400 microns. Moreparticularly, the dry film thickness of the top coat should be about 20to 150 microns. In one embodiment, more than one top coat is applied tothe metal surface.

The top coat is completely cured after application using methods knownin the art, including, but not limited to, heating and UV light. In oneembodiment, the top coat is cured by a method selected from the groupconsisting of a heating means, short or medium long wave infrared light,and a combination of a heating means and infrared light. In oneembodiment, the primer is cured using a heating means with ovens thatreach a peak metal temperature of 370-450° F., with an oven dwell timeof 30-300 seconds. More particularly, the primer is cured using aheating means with ovens that reach a peak metal temperature of 400-420°F., with an oven dwell time of 60-180 seconds. In one embodiment, theheating means is an electric or natural gas convection oven.

Forming and Plating the Metal Article

Once the surface of the metal article has been coated, it can behandled, stacked, stored, or shipped. In one embodiment, the coatedmetal article is one side of a metal blank. In one embodiment, theuncoated front side of the metal article can be flat polished to thedesired surface finish, as shown by Step 80 in FIG. 1, followed by beingformed into its desired three-dimensional shape, as shown by Step 90 inFIG. 1. For some articles, the coated side will become the back side ofthe article, and additional processing, including, but not limited to,plating with one or more metals, will be performed on the front side.Articles may be formed by processes known in the art, including, but notlimited to, stamping, bending, or using forming dies.

A non-limiting example of an article that can be formed is a motorvehicle bumper. The uncoated front side of the metal article can bepolished to provide a smooth, unblemished metal surface, as shown byStep 80 in FIG. 1. Before plating, the uncoated surface of the bumpercan be cleaned by immersion soaking, cathodic cleaning, and anodiccleaning, using methods well known in the art. In each of the cleaningsteps, depicted by Step 100 in FIG. 1, the cleaning fluid of 9%potassium hydroxide concentration is held between 165-180° F. Aftercleaning the uncoated surface of the metal, the coated surface of thebumper should not show any blistering, delamination, or color fading.After cleaning, the bumper can be packaged and shipped, or a platedmetal coating can be added to the uncoated surface.

The uncoated surface of the bumper can be plated according to methodswell known in the art. This process is depicted by Step 110 in FIG. 1.Appropriate metals for plating include, but are not limited to, nickeland chrome. For a motor vehicle bumper, only the front side of thebumper needs to be treated, as the back side has the coating of thepresent invention as a corrosion barrier. Once plating is complete, thebumper can be packaged and shipped or installed on a motor vehicle.

In one embodiment, the metal article is formed into a three-dimensionalarticle with opposing front and back sides. In another embodiment, themetal surface that is coated is one side of a metal sheet. Moreparticularly, in one embodiment, the back side of the metal sheet iscoated and the front side is electroplated with one or more layers of ametallic plating element.

More particularly, in one embodiment, the metal article is a bumper fora motor vehicle. FIG. 1 is a flowchart that illustrates a manufacturingprocess for making a metal motor vehicle bumper. First, a metal blank isselected, as shown in Step 10. The surface that will be the back of themetal bumper is cleaned, as shown in Step 30. Then, in Step 40, thesurface is pretreated. A sealer is applied in Step 50, followed by aprimer in Step 60. In Step 70, a top coat is applied. In one embodiment,the surface of the metal is ground before cleaning, as shown in Step 20.In another embodiment, the uncoated side of the metal is cleaned andpolished to a desired surface finish before being pressed into a threedimensional shape. This is depicted in Step 80. In another embodiment,the metal is formed into a desirable shape. This is depicted in Step 90.In an additional embodiment, the metal can be electrochemically cleanedand electroplated with one or more metals, as shown in Steps 100-110.

It is possible, however, that one or more steps depicted in FIG. 1 maybe repositioned, removed, or otherwise modified. It is envisioned thatalternate methods of accomplishing the method of the present inventionmay be adopted without deviating from the invention as portrayed.

Described below are specific examples relating to the process forcoating metal components according to the present invention. Alsodisclosed are several tests that were undertaken to evaluate theeffectiveness of the coating of the present invention. The examples areprovided so the invention may be more fully understood and are not meantto limit the scope of the invention in any way.

EXAMPLES Example 1 Application of Coating

This example is directed to a process for producing a metal motorvehicle bumper by selecting a flat metal blank, applying a coating tothe back side surface of the metal blank, and then using a multi-stepstamping process to form the flat metal blank into the desired shape.

For this example, a flat, cold rolled steel blank that was 23 incheswide, 102 inches long, and 0.063 inches thick was selected for coating.The selected flat, cold rolled steel blank was then placed on a coatingline that was equipped with an abrasion station, a pretreatment station,a primer application station, a top coat application station, and agas-fired cure oven. This coating line was designed to abrade, clean,pretreat, and prime the metal blank.

When the blank was placed on the coating line, it was first abradedusing standard techniques known in the metal finishing art. After thisstep, the selected metal blank was cleaned with a water-borne alkalinecleaner at 150° F., which was applied by surface spraying using spraynozzles. The metal blank was then treated with a water-borne ironphosphate pretreatment at 150° F., which was applied by surface sprayingusing spray nozzles. The coating weight of the iron phosphatepretreatment applied to the metal blank was 20 mg/ft². The ironphosphate pretreatment was sealed with a water-borne non-chromedry-in-place sealer, which was applied by roll coating the surface. Thedry-in-place sealer was then dried using ambient air. The coating weightof the non-chrome sealer was 16 mg/ft².

After the sealer was applied, the metal blank was primed with a graypolyester/urethane chrome-free primer, which was applied using airassisted airless spray guns to achieve the desired wet film build. Afterthe primer was applied, the coating line was stopped, and the metalblank was removed. After a one minute flash time at ambient temperature,it was placed in the gas-fired cure oven, which was set to 625° F., forabout 2.5 minutes, which allowed the metal to reach the peak metaltemperature of about 420° F. After about 2.5 minutes in the gas-firedcure oven, the blank was removed and allowed to cool. To ensure that theprimer had been fully cured, the solvent resistance of the coating waschecked using the standard MEK double rub test method, described in thecoating industry as ASTM Test Method D5402-06. The number of double rubsfor the material should be between 10 to 25, indicating that the primerhas been fully cured. In this example, the MEK double rub was 14. Thedry film build of the primer layer was 12.7 microns, which was measuredusing an elcometer.

After the metal blank had been allowed to cool to ambient temperature,it was loaded back onto the coating line at the top coat applicationstation. Once loaded, the line was powered on, and the blank was passedunder a curtain coater to apply the desired black PVC top coat and thedesired wet film build. After a one minute flash time at ambienttemperature, it was placed in the gas-fired cure oven, which was set to625° F., for about 2.5 minutes, which allowed the metal to reach thepeak metal temperature of 420° F. After 2.5 minutes in the gas-firedcure oven, the blank was removed and allowed to cool to ambienttemperature. The dry film build of the PVC top coat was 89 microns,which was measured using an elcometer.

Quality Control Testing

After the PVC top coat was applied, the coated metal blank was subjectedto a series of tests to determine the quality of the coating. In thisexample, the primer/top coat coating had a gloss of 20 at 60° using agloss meter. The coating system also demonstrated a pencil hardness ofB. The blank exhibited no cracking when bent over a mandrel. It showedno cracking or delaminating from the metal substrate when subjected todeforming of the metal and coating with a ball and ring press. Afterfour hours of submersion in boiling water, the deformed, coated blankshowed no blistering or loss of adhesion.

Bumper Formation

Once the coating had passed all quality control tests, the uncoatedsurface of the metal blank was polished using common metal polishingtechniques that are well known in the art. After polishing, both thetreated and the untreated sides of the metal blank were washed andtreated with zinc phosphate. A die lube was then applied.

The blank was then placed in a stamping die, so that the coated side ofthe metal blank would be on the back side of the metal bumper in itsfinal formed state and the polished side of the blank would be on thefront side of the metal bumper in its final formed state. Typically, thefirst die defines the general shape of the bumper. The coating on theback side of the selected metal blank was subjected to about 500 to 1000tons of force in the first forming step. After this first forming step,the coating on the back side showed no cracking, color change, or lossof adhesion to the metal.

The formed metal blank was then allowed to continue through theremaining press dies, where excess metal was trimmed away, notches andholes were punched in to the bumper for mounting brackets and fog lamps,and more definition was added to the shape of the metal bumper. Afterall of these subsequent forming steps, the coating on the back side ofthe bumper did not show any signs of tearing, fraying, cracking, ordelaminating.

The final formed bumper was then cleaned using conventional methods thatare well known in the art.

Plating the Metal Bumper

The formed bumper was then mounted on a rack for electrochemicalcleaning of the metal surface, followed by electrochemical plating ofthe bare metal surface with a layer of nickel and then a layer ofchrome. The process for the electrochemical cleaning and metal platingof the bumper is a standard process that is well documented in the art.

Inspection of Metal Bumper and Coating

The bumper was then inspected for any blistering, delaminating of thecoating, or nickel and chrome deposits on the back side of the bumper.The primer/PVC coating did not show any signs of failure after theelectrochemical cleaning and plating steps. There was no evidence ofblistering, delaminating, peeling, or fracturing of the coating on theback side of the bumper. Additionally, there was no evidence of nickelor chrome plating that had penetrated the primer/PVC coating. There wasvery little nickel and chrome build-up on edges, holes, and punch outson the bumper, which indicated that the nickel and chrome did not adhereto the PVC coating.

Other Embodiments

The foregoing disclosure has been described in some detail by way ofillustration and example, for purposes of clarity and understanding. Theinvention has been described with reference to various specific andpreferred embodiments and techniques. However, it should be understoodthat many variations and modifications can be made while remainingwithin the spirit and scope of the invention. It will be obvious to oneof skill in the art that changes and modifications can be practicedwithin the scope of the appended claims. Therefore, it is to beunderstood that the above description is intended to be illustrative andnot restrictive.

The scope of the invention should, therefore, be determined not withreference to the above description, but should instead be determinedwith reference to the following appended claims, along with the fullscope of equivalents to which such claims are entitled.

1. A method of coating the surface of a metal article, comprising thesteps of: a. cleaning the metal surface with one or more alkalinecleaners; b. pretreating the metal surface with one or morephosphate-containing pretreating compounds; c. applying one or morecorrosion-resistant sealers to the metal surface; d. applying one ormore corrosion-resistant primers to the metal surface; and e. applyingone or more chemical- and corrosion-resistant top coats to the metalsurface, wherein the resulting metal surface is chemical-, corrosion-,and abrasion-resistant.
 2. The method of claim 1, wherein the metalarticle is selected from the group consisting of pre-formed metalobjects and metal blanks with a thickness between 0.001 and 5 inches. 3.The method of claim 1, wherein the metal article comprises a materialselected from the group consisting of brushed or unbrushed hot rolledsteel, brushed or unbrushed cold rolled steel, and brushed or unbrushedhigh strength steel.
 4. The method of claim 3, wherein the metal articlecomprises a material selected from the group consisting of DrawingSteel, Deep Drawing Steel, Extra Deep Drawing Steel, and High StrengthLow Alloy Steel.
 5. The method of claim 1, further comprising the stepof grinding the surface of the metal article to provide an abradedsurface that is free of residue, oil, and grease.
 6. The method of claim1, wherein the surface of the metal article is cleaned by a processselected from the group consisting of cleaning in a vat and cleaning bysurface spraying and scrubbing, and combinations thereof, using acleaner selected from the group consisting of Betz Kleen 132®, 111 LowFoam Cleaner®, and mixtures thereof.
 7. The method of claim 1, whereinthe surface of the metal article is pretreated with aphosphate-containing pretreating compound selected from the groupconsisting of chromic phosphate, ferrous phosphate, ferric phosphate,zinc phosphate, and mixtures thereof.
 8. The method of claim 7, whereinthe surface of the metal article is pretreated with a material selectedfrom the group consisting of Permatreat® 1510, Permatreat® 2105,Bonderite 902, Bonderite 2010, ChemCote 3010, Gardobond 51/2,Permatreat® 407, and mixtures thereof.
 9. The method of claim 1, whereinthe pretreating compound is applied by a process selected from the groupconsisting of spraying the metal, dipping the metal, brush coating themetal, roll coating the metal, and combinations thereof, to a coatingweight of 10-100 mg/ft².
 10. The method of claim 1, wherein the sealeris selected from the group consisting of chrome sealers selected fromthe group consisting of Betz Sealguard™ 750, Bonderite 1402W, GardobondC 4571, and mixtures thereof, and non-chrome sealers, selected from thegroup consisting of Betz® DC2068, Bonderite 1455 SF, and mixturesthereof.
 11. The method of claim 1, wherein the sealer is applied by aprocess selected from the group consisting of dipping the metal, rollcoating the metal, spraying the metal, brush coating the metal, andcombinations thereof, to a coating weight of 2-50 mg/ft².
 12. The methodof claim 1, wherein the primer is selected from the group consisting ofwater borne primers, solvent borne primers, liquid solvent borne highsolids primers, powder primers, and mixtures thereof.
 13. The method ofclaim 12, wherein the primer comprises a material selected from thegroup consisting of thermoplastic acrylic, polyester, polyvinyl,polyepoxy, polyurethane, polyamide, polyamine, acrylic carbamate resinsystems, and mixtures thereof.
 14. The method of claim 13, wherein theprimer comprises curable resin with functional groups that are selectedfrom the group consisting of hydroxyl, carboxylic acid, carbamate,anhydride, amine, epoxy, amide, carbonate, and mixtures thereof, whereinthe functional groups of the primer are reacted with a crosslinkingagent selected from the group consisting of isocyanates, blockedisocyanates, aminoplasts, melamines, epoxies, anhydrides, and mixturesthereof.
 15. The method of claim 14, wherein the primer is a polyesterresin system that contains hydroxyl groups that are crosslinked withblocked or unblocked isocyanates, or combinations thereof.
 16. Themethod of claim 1, wherein the viscosity of a solvent borne primer isadjusted with a standard organic solvent selected from the groupconsisting of ketones, acetates, non polar aliphatic hydrocarbons, polaraliphatic hydrocarbons, polar aromatic solvents, non-polar aromaticsolvents, alkyl polyethers, alkyl polyether acetates, and mixturesthereof, so that the viscosity of the primer is 20-40 seconds using aZahn #2 viscosity cup.
 17. The method of claim 1, wherein the primercontains one or more pigments selected from the group consisting ofchrome and non-chrome pigments, wherein the pigment is selected from thegroup consisting of carbon black pigment, titanium dioxide, iron oxide,chrome yellow, moly orange, titanium yellow, nickel titanate yellow,chrome green, phathalo blue, phathalo green, perylene red, magenta red,and mixtures thereof.
 18. The method of claim 1, wherein the primer isapplied by a process selected from the group consisting of air atomizedspray, air assisted airless spray, airless spray, HVLP spray,electrostatic rotary bell spray, electrostatic air atomized spray,electrostatic air assisted airless spray, electrostatic HVLP spray,direct roll coating, reverse roll coating, flow coating, dipping,curtain coating, and combinations thereof, to a dry film thickness of2.5 microns to 50 microns.
 19. The method of claim 1, wherein the primeris cured by a method selected from the group consisting of a heatingmeans, short or medium long wave infrared light, and a combination of aheating means and infrared light.
 20. The method of claim 19, whereinthe primer is cured using a heating means with ovens that reach a peakmetal temperature of 370-450° F., with an oven dwell time of 30-300seconds.
 21. The method of claim 1, wherein the top coat is selectedfrom the group consisting of thermoplastic or thermoset water borne,solvent borne, solvent borne high solid, powder coating based onacrylic, polyester, epoxy, urethane, polyamide, polyamine, carbamate,polyvinylidine fluoride resin systems, and mixtures thereof.
 22. Themethod of claim 21, wherein the top coat is selected from the groupconsisting of colloidal dispersions of polyvinyl chloride formulatedwith plasticizers selected from the group consisting of phthalate andnon-phthalate based materials, and mixtures thereof.
 23. The method ofclaim 22, wherein the top coat is a PVC plastisol coating.
 24. Themethod of claim 1, wherein the top coat is selected from the groupconsisting of UV cured coatings and Electron Beam cured coatings. 25.The method of claim 1, wherein the viscosity of the solvent borne topcoat is adjusted with water, nonpolar mineral spirits, or a standardorganic solvent selected from the group consisting of ketones, acetates,non polar aliphatic hydrocarbons, polar aliphatic hydrocarbons, polararomatic solvents, non-polar aromatic solvents, alkyl polyethers, alkylpolyether acetates, and mixtures thereof, so that the viscosity of thetop coat is 15-40 seconds using a Zahn #4 viscosity cup.
 26. The methodof claim 1, wherein the top coat is pigmented with one or more coloredpigments selected from the group consisting of inorganic pigmentsinorganic pigment selected from the group consisting of zinc white, zincsulfide, carbon black, iron manganese black, spinel black, chromiumoxide, chromium oxide hydrate green, cobalt green, ultramarine green,cobalt blue, ultramarine blue, manganese blue, ultramarine violet,cobalt violet, manganese violet, red iron oxide, molybdate red,ultramarine red, brown iron oxide, mixed brown iron oxide, yellow ironoxide, nickel titanium yellow, chromium titanium yellow, cadmiumsulfide, cadmium zinc sulfide, chromium yellow, bismuth vanadate, andmixtures thereof, and organic pigments selected from the groupconsisting of manoazo pigments, diazo pigments, anthraquinone pigments,bexnzimidazole pigments, quinacridone pigments, quinophthalone pigments,diteopyrrolopyrrole pigments, dioxzine pigments, indanthrone pigments,isoindolien pigments, isoindolinone pigments, azomethine pigments,perinone pigments, perylene pigments, phthalocyanine pigments, anilineblack, and mixtures thereof.
 27. The method of claim 1, wherein the topcoat is applied by a process selected from the group consisting of airatomized spray, air assisted airless spray, airless spray, HVLP spray,electrostatic rotary bell spray, electrostatic air atomized spray,electrostatic air assisted airless spray, electrostatic HVLP spray,direct roll coating, reverse roll coating, flow coating, dipping,curtain coating, and combinations thereof, to a dry film thickness of2.5-400 microns.
 28. The method of claim 1, wherein the top coat iscured by a method selected from the group consisting of a heating means,short or medium long wave infrared light, and a combination of a heatingmeans and infrared light.
 29. The method of claim 28, wherein the topcoat is cured using a heating means with ovens that reach a peak metaltemperature of 370-450° F., with an oven dwell time of 30-300 seconds.30. The method of claim 1, wherein the metal article is one side of ametal sheet.
 31. The method of claim 1, further comprising forming themetal surface into a three-dimensional article with opposing front andback sides.
 32. The method of claim 1, wherein the front side of themetal sheet is polished.
 33. The method of claim 32, wherein the backside of the metal sheet is coated and the front side is plated with oneor more layers of a metallic plating element.
 34. The method of claim 1,wherein the metal article is a bumper for a motor vehicle.
 35. A methodof coating the surface of a metal article, comprising the steps of a.cleaning the metal surface with Betz Kleen 132® or 111 Low FoamCleaner®; b. pretreating the metal surface with one or more pretreatingcompounds selected from the group consisting of Permatreat® 1510,Permatreat® 2105, Bonderite 902, Bonderite 2010, ChemCote 3010,Gardobond 51/2, and Permatreat® 407; c. applying Bonderite 1455 SF tothe metal surface; d. applying a polyester resin primer system thatcontains hydroxyl groups that are crosslinked with blocked or unblockedisocyanates; and e. applying a PVC plastisol top coat coating, whereinthe resulting coated metal surface is chemical-, corrosion-, andabrasion-resistant.
 36. The method of claim 35, further comprising thestep of plating the front side of the metal sheet with one or morelayers of a metallic plating element
 37. A metal motor vehicle bumper,wherein the metal bumper characterized by a surface that is: a. cleanedwith Betz Kleen 132® or 111 Low Foam Cleaner®; b. pretreated with one ormore pretreating compounds selected from the group consisting ofPermatreat® 1510, Permatreat® 2105, Bonderite 902, Bonderite 2010,ChemCote 3010, Gardobond 51/2, and Permatreat® 407; c. sealed withBonderite 1455 SF; d. coated with a polyester resin primer system thatcontains hydroxyl groups that are crosslinked with blocked or unblockedisocyanates; and e. coated with a PVC plastisol top coat; wherein theresulting metal motor vehicle bumper has a chemical-, corrosion-, andabrasion-resistant coating.
 38. The metal bumper of claim 37, whereinonly the back side of the metal motor vehicle bumper is coated.
 39. Themetal object of claim 38, further comprising one or more layers of ametallic plating element on the front side of the metal motor vehiclebumper.